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authorHans Verkuil <hverkuil-cisco@xs4all.nl>2019-08-15 16:44:52 +0200
committerHans Verkuil <hverkuil-cisco@xs4all.nl>2019-08-17 10:24:37 +0200
commitbf7ca7e0046e7f4e246876e9cfab5a65ca1ec72a (patch)
treefee0c69a171eccdf2cde449dc74f43b6ea68f9b9
parent5a305f4833eb4124168eb8c5cb87f33902e39ef7 (diff)
pixfmt-compressed.rst: improve H264/HEVC/MPEG1+2/VP8+9 documentationbr-v5.4l
The existing documentation was incorrect and did not correspond to how actual codec drivers implemented this. Update the documentation to explicitly specify what is actually expected. Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
-rw-r--r--Documentation/media/uapi/v4l/pixfmt-compressed.rst36
1 files changed, 30 insertions, 6 deletions
diff --git a/Documentation/media/uapi/v4l/pixfmt-compressed.rst b/Documentation/media/uapi/v4l/pixfmt-compressed.rst
index 493b6020107d..292fdc116c77 100644
--- a/Documentation/media/uapi/v4l/pixfmt-compressed.rst
+++ b/Documentation/media/uapi/v4l/pixfmt-compressed.rst
@@ -41,7 +41,12 @@ Compressed Formats
- ``V4L2_PIX_FMT_H264``
- 'H264'
- - H264 video elementary stream with start codes.
+ - H264 Access Unit.
+ The decoder expects one Access Unit per buffer.
+ The encoder generates one Access Unit per buffer.
+ If :ref:`VIDIOC_ENUM_FMT` reports ``V4L2_FMT_FLAG_CONTINUOUS_BYTESTREAM``
+ then the decoder has no requirements since it can parse all the
+ information from the raw bytestream.
* .. _V4L2-PIX-FMT-H264-NO-SC:
- ``V4L2_PIX_FMT_H264_NO_SC``
@@ -89,12 +94,20 @@ Compressed Formats
- ``V4L2_PIX_FMT_MPEG1``
- 'MPG1'
- - MPEG1 video elementary stream.
+ - MPEG1 Picture. Each buffer starts with a Picture header, followed
+ by other headers as needed and ending with the Picture data.
+ If :ref:`VIDIOC_ENUM_FMT` reports ``V4L2_FMT_FLAG_CONTINUOUS_BYTESTREAM``
+ then the decoder has no requirements since it can parse all the
+ information from the raw bytestream.
* .. _V4L2-PIX-FMT-MPEG2:
- ``V4L2_PIX_FMT_MPEG2``
- 'MPG2'
- - MPEG2 video elementary stream.
+ - MPEG2 Picture. Each buffer starts with a Picture header, followed
+ by other headers as needed and ending with the Picture data.
+ If :ref:`VIDIOC_ENUM_FMT` reports ``V4L2_FMT_FLAG_CONTINUOUS_BYTESTREAM``
+ then the decoder has no requirements since it can parse all the
+ information from the raw bytestream.
* .. _V4L2-PIX-FMT-MPEG2-SLICE:
- ``V4L2_PIX_FMT_MPEG2_SLICE``
@@ -135,7 +148,9 @@ Compressed Formats
- ``V4L2_PIX_FMT_VP8``
- 'VP80'
- - VP8 video elementary stream.
+ - VP8 compressed video frame. The encoder generates one
+ compressed frame per buffer, and the decoder requires one
+ compressed frame per buffer.
* .. _V4L2-PIX-FMT-VP8-FRAME:
- ``V4L2_PIX_FMT_VP8_FRAME``
@@ -160,12 +175,19 @@ Compressed Formats
- ``V4L2_PIX_FMT_VP9``
- 'VP90'
- - VP9 video elementary stream.
+ - VP9 compressed video frame. The encoder generates one
+ compressed frame per buffer, and the decoder requires one
+ compressed frame per buffer.
* .. _V4L2-PIX-FMT-HEVC:
- ``V4L2_PIX_FMT_HEVC``
- 'HEVC'
- - HEVC/H.265 video elementary stream.
+ - HEVC/H.265 Access Unit.
+ The decoder expects one Access Unit per buffer.
+ The encoder generates one Access Unit per buffer.
+ If :ref:`VIDIOC_ENUM_FMT` reports ``V4L2_FMT_FLAG_CONTINUOUS_BYTESTREAM``
+ then the decoder has no requirements since it can parse all the
+ information from the raw bytestream.
* .. _V4L2-PIX-FMT-FWHT:
- ``V4L2_PIX_FMT_FWHT``
@@ -173,6 +195,8 @@ Compressed Formats
- Video elementary stream using a codec based on the Fast Walsh Hadamard
Transform. This codec is implemented by the vicodec ('Virtual Codec')
driver. See the codec-fwht.h header for more details.
+ :ref:`VIDIOC_ENUM_FMT` reports ``V4L2_FMT_FLAG_CONTINUOUS_BYTESTREAM``
+ since the decoder can parse all the information from the raw bytestream.
* .. _V4L2-PIX-FMT-FWHT-STATELESS:
- ``V4L2_PIX_FMT_FWHT_STATELESS``

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